Double Eccentric Flange Butterfly Valve, Metal Seated
Engineered for demanding industrial applications requiring zero leakage and exceptional durability, the Metal Seated Double Offset Flanged Butterfly Valve represents the pinnacle of high-performance flow control. This robust valve design is specifically built to handle extreme temperatures, abrasive media, and high-pressure differentials where resilient seated valves would fail. The core technology lies in its double eccentric (double offset) disc and stem configuration, which fundamentally eliminates sliding friction between the metal seat and disc during operation. This crucial feature ensures smooth, low-torque actuation and dramatically extends the service life of the sealing components. For critical isolation duties in the oil & gas, power generation, chemical processing, and marine industries, this valve provides a reliable, long-term solution with superior sealing integrity. The hard-faced metal-to-metal seat ensures tight shut-off even under the most severe service conditions.
The design of the Double Eccentric Flange Butterfly Valve, Metal Seated employs two distinct offsets: the first offset positions the stem axis behind the centerline of the disc seat, and the second offset places it slightly off-center to the pipeline bore. This geometric principle causes the disc to lift away from the seat immediately upon the first few degrees of rotation, transitioning from a sealing to a cam-like motion. This action minimizes wear and allows the valve to achieve bubble-tight shut-off repeatedly. The flanged ends, typically designed to ASME, DIN, or other international standards, ensure easy and secure installation into existing piping systems. Standard body materials include carbon steel (WCB), stainless steel (CF8/CF8M), and special alloys, with the disc and seat often hard-coated or overlaid with materials like Stellite, Hastelloy, or 316 stainless steel to resist corrosion, erosion, and galling.
Technical Specifications & Design Features
- Design & Construction: Double eccentric (double offset) design, flanged ends, metal seated.
- Size Range: 3" (DN80) to 48" (DN1200) and larger.
- Pressure Rating: ANSI Class 150 to Class 600 (PN10 to PN100).
- Temperature Range: -50°C to +600°C (-58°F to +1112°F), depending on seat and body materials.
- Seat & Disc: Hard-faced metal-to-metal seat (e.g., Stellite on 13Cr/316SS); disc often coated with compatible hard material.
- Body Materials: Carbon Steel (A216 WCB), Stainless Steel (A351 CF8/CF8M), Duplex Stainless Steel, Special Alloys.
- Stem: One-piece forged stem, typically 17-4PH, 316SS, or 416SS, with blow-out proof design.
- Sealing: Primary seal: Metal seat. Secondary stem seals: Graphite or PTFE packing.
- Operation: Manual (lever, gear), Pneumatic, Electric, or Hydraulic actuation.
- Standards: API 609, ISO 10631, ASME B16.34, Fire Safe per API 607/API 6FA.
| Size (inch) | ANSI Class | Standard Body Material | Standard Seat/Disc Material | Typical Applications |
|---|---|---|---|---|
| 3" - 12" | 150, 300 | WCB, CF8 | 13Cr/Stellite, 316SS | Process Lines, Hot Water, Steam |
| 14" - 24" | 150, 300 | WCB, CF8M, Duplex | 316SS/Stellite, Alloy 20 | Oil & Gas Pipelines, Seawater, Chemicals |
| 26" - 48" | 150, 300, 600 | WCB, LCB, CF8M | Stellite overlay, Monel | Power Plant FGD, Main Steam Isolation, Large Water Mains |
Operational Parameters & Performance Data
| Parameter | Specification / Detail |
|---|---|
| Flow Characteristic | Approximately equal percentage; provides good control over a wide range. |
| Leakage Rate | Meets or exceeds ANSI/FCI 70-2 Class IV (Metal Seated) or Class VI (with soft secondary seat if equipped). |
| Torque Requirement | Low operating torque due to offset design; specific torque varies with size, pressure, and actuator type. |
| End Connection Standards | RF or RTJ flanges per ASME B16.5, ASME B16.47, DIN, EN, JIS, etc. |
| Face-to-Face Dimensions | Complies with API 609, ISO 5752, or customer specifications. |
| Fire Safe Design | Available with API 607/API 6FA certification, maintaining seal integrity during and after fire exposure. |
| Cavitation & Erosion Resistance | Superior resistance due to hard-faced seating surfaces and streamlined disc design. |
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